This invention relates to the packaging of articles with a continuous length of heat sealable film, that is, a film that is sealable by heat and pressure, which may be either of a single material or a lamination of two or more plies of similar or dissimilar materials. The invention is directed more specifically to a method of, and apparatus for, packaging articles of various sizes without waste of the film.
The packaging of foods and other articles with heat sealable film is carried out by a "instant sealing method" or an "extended period sealing method". The "instant sealing method" calls for the use of a rotary sealer which rotates constantly, while being heated to a required temperature, for instantly heat sealing thin films. Although well suited for efficiently packaging relatively small sized articles, this technique is not adoptable for the packaging of larger or heavier articles with thicker films or laminations of dissimilar materials. The "extended period sealing method" which is necessary for these packaging media as most of them requires the application of heat and pressure for a longer period of time.
A packaging line employing the "extended period sealing method" has been known. Fed at a constant speed, a continuous length of heat sealable film is folded longitudinally over successive articles with constant spacings therebetween. The lapping side edges of the folded film are heat sealed over the articles. Thereafter, the folded and side sealed film is sealed at points intermediate the successive articles received therein through the "extended period sealing method". The film is so sealed while traveling along a linear track by endless rows of end sealing means.
A problem has existed with this conventional type of packaging line. The packages produced as above have been constant in length regardless of the size of the articles. The length of each package has been determined by the spacings of the end sealing means for heat sealing the film at points intermediate thereof and has not been variable without changing the spacings of the end sealing means. This of course involves waste of the film as spacings between the end sealing means have been determined in consideration of maximum size articles to be packaged. To adjust the spacings to each size of articles is to add to human task and to decrease the production of the machine.